Objective: To evaluate the effect of 0.5% tropicamide/0.5% phenylephrine mixed eye drop and make the inter-eye comparison of refractive outcomes in Chinese adults with myopia.
Methods: Refractive measurements were performed without cycloplegia and repeated 30 minutes later with 0.5% tropicamide/0.5% phenylephrine mixed eye drop (Mydrin-P*) on 341 myopic adults. Vector analysis was used to analyze the data. Changes of spherical equivalent (M) and astigmatism for both J0 and J45 components between these two refractions were calculated as Error_M, Error_J0 and Error_J45. Inter-eye correlations were studied. The inter-eye difference after cycloplegics were described as Diff M, Diff J0 and Diff J45. The effect of anisometropia, age and the higher order aberrations (HOAs) on inter-eye differences toward the cycloplegic agent were analyzed.
Results: Difference was found only for the Error_J45 component between the two eyes (p=0.0040). Pearson correlation coefficients between the two eyes for Error_M, Error_J0, and Error_J45 were 0.3140 (p<0.0001), 0.1464 (p=0.0068), and 0.0099 (p=0.8558), respectively. The inter-eye differences (Diff) in response to cycloplegic agent increased with the amount of anisometropia. The oldest group had the highest Diff M values. However, HOAs were found not to be related to the inter-eye differences.
Conclusions: Accommodation was still relaxed by tropicamide/phenylephrine eye drops in myopic adults. The changes of refraction due to cycloplegia were not well correlated between the two eyes in myopic patients. Anisometropia and ocular dominance might be an important factor for the inter-eye difference.